Carbonless copy paper

Abstract

Carbonless copy paper is prepared by placing a first sheet of paper coated on one side with a hydrophilic colloid solution in which are dispersed microcapsules of oil droplets containing a colorless electron donor dye into contact with a second sheet of paper coated with an absorbent and an electron accepting color developer compound. The heat resistance and moisture resistance of the copy paper is substantially improved by adding to the hydrophilic colloid solution a graft copolymer having a backbone of carboxymethyl cellulose or gum arabic and side chains of polyacrylic acid or polymethacrylic acid. The image response time of the second sheet can be improved by adding pectin or sulfated starch to the coating.

We claim: 
     
       1. A pressure-sensitive color transfer sheet containing an electron donating chromogenic color former for use in combination with a second sheet containing an electron accepting color developer, said color former being dispersed in substantially cluster-free microcapsule form in a hydrophilic colloid solution containing a water soluble graft copolymer having a backbone of carboxymethyl cellulose or gum arabic and side chains of polyacrylic acid or polymethacrylic acid, said side chains comprising from 5 to 10 percent by weight of said copolymer. 
     
     
       2. A pressure-sensitive color transfer sheet according to claim 1 wherein the hydrophilic colloid solution comprises gelatin and the graft copolymer. 
     
     
       3. A pressure-sensitive color transfer sheet according to claim 2 wherein the amount of graft copolymer is within the range of 1/8 to 1/4 by weight of the amount of gelatin. 
     
     
       4. A carbonless copy paper color transfer system comprising a pressure-sensitive color transfer sheet having one side coated with a layer containing an electron donating chromogenic color former, said layer being in contact with a second layer coated on a second sheet, said second layer containing an electron accepting color developer, said color former being dispersed in substantially cluster-free microcapsule form in a hydrophilic colloid solution containing a water soluble graft copolymer having a backbone of carboxymethyl cellulose or gum arabic and side chains of polyacrylic acid or polymethacrylic acid, said side chains comprising from 5 to 10 percent by weight of said copolymer. 
     
     
       5. A carbonless copy paper according to claim 4 wherein the hydrophilic colloid solution comprises gelatin and the graft copolymer. 
     
     
       6. A carbonless copy paper according to claim 5 wherein the amount of graft copolymer is within the range of 1/8 to 1/4 by weight of the amount of gelatin. 
     
     
       7. A carbonless copy paper according to claim 4 wherein the second layer containing the color developer also contains pectin or sulfated starch. 
     
     
       8. A carbonless copy paper according to claim 4 wherein the color developer is p-phenyl phenol formaldehyde resin.